Improving the properties of alumina castable refractories by using silica-sol as binding agent

In this research, the effect of silica sol on various properties of Al۲O۳–SiC–C based castable refractories was studied using both cement and sol bonding systems. The microstructure, as well as the physical and mechanical properties of low-cement and non-cement alumina castable refractories, were investigated. Different castable compositions were processed and heated at ۹۰۰°C and ۱۵۰۰°C. Four cement-containing batches were made using a simple tapping technique in standard cubic molds (۵۰×۵۰×۵۰ mm). Equivalent to their composition, four non-cement batches were prepared using silica sol as bonding agent instead of cement, and their performances were compared at two sintering temperatures (۹۰۰°C and ۱۵۰۰°C) in terms of bulk density (BD), apparent porosity (AP), cold crushing strength (CCS), and X-ray diffraction (XRD). The improvement in properties of non-cement samples was confirmed through these measures. Removing the cement and replacing it by silica sol, made a reduction in the amount of porosity, and as a result, the bulk density increased in non-cement batches due to the coaxial and ultrafine morphology of silica sol, especially for the samples which heated at ۱۵۰۰°C. Phase analysis (XRD) of these samples confirmed the presence of corundum as the main phase, with mullite, carbon, silicon carbide, and spinel as minor phases. Mullite phase was responsible for the higher values of cold crushing strength in non-cement castable refractories.

کلیدواژه ها:

Castable refractory ، Fused Alumina ، Tabular Alumina ، Silica Sol ، Calcium Aluminate ، Cement ، Mullite